diff --git a/hosts/common/optional/docker/default.nix b/hosts/common/optional/docker/default.nix
index e289208..b6dba80 100644
--- a/hosts/common/optional/docker/default.nix
+++ b/hosts/common/optional/docker/default.nix
@@ -6,6 +6,8 @@
     pkgs.arion
   ];
 
+  # Arion works with Docker, but for NixOS-based containers, you need Podman
+  # since NixOS 21.05.
   virtualisation = {
     podman = {
       enable = true;